Lack of ingestive compensation to osmotic stimuli in chronic decerebrate rats

Chronic decerebrate rats fitted with oral fistulas for remote injection of water or nutrient were tested for their capacity to behaviorally compensate for dehydration by increasing their ingestion of water. Decerebrates and their controls were given water for ingestion via the oral fistula in 50-microliter aliquots following various challenges. The rats' ejection of water from the mouth marked behavioral termination of the drinking. The volume of water was measured 1 and 24 h after an intragastric meal of regular diet; 0.5, 4, 8, and 24 h following subcutaneous isotonic or hypertonic NaCl injection; and 1, 4, 8, and 24 h following an intragastric meal of regular or 3% NaCl adulterated diet. Unlike controls, decerebrates failed to increase the amount of water ingested following intracellular dehydration regardless of the means of producing dehydration or the duration of time permitted for a response. However, both control and decerebrate rats increased their ingestion of a sweet solution (0.03 M sucrose) demonstrating their capacity to respond and confirming their ability to compensate for food deprivation. This lack of increased water intake in response to dehydration for decerebrate rats favors the existence of at least some aspects of the regulatory circuitry for this behavioral control of water balance to lie in the forebrain.